As you can see in Fig.38, I got a correct refraction just by adding a shell modifier.

Fig.38

I needed to enable the refraction "effects". If you wanted a better effect, you could also enable the Reflection on Back Side option. This will compute reflection on the back side of the surface normal, which means that you will get reflections appearing inside the glass object (Fig.39).

Fig. 39

To change the color of the glass, like a shell of a tail light, I didn't adjust the refraction color, which is used to control the power of refraction, but I adjusted the fog color and fog multiplier (Fig.40 - 41).